1. Field of the Invention
The present invention relates to a light emitting body, light emitting element and light emitting display device using the same and more particularly to the light emitting body and light emitting element which can secure practical light emission lasting time and to the light emitting display device using the light emitting body and light emitting element.
The present application claims priority of Japanese Patent Application No.2001-051410 filed on Feb. 27, 2001, which is hereby incorporated by reference.
2. Description of the Related Art
Generally, as a self-emitting body used for a display device, a field mission device and an electroluminescence (EL) device are available. The EL device can be classified into two types of devices, one being an organic EL device using an organic material as a light emitting layer and another being an inorganic EL device using an inorganic material as the light emitting layer.
The organic EL device is generally made up of an anode, a cathode and a super-thin film organic EL layer made of an organic light emitting compound and being sandwiched between the anode and the cathode. When a voltage is applied between the anode and cathode, a hole is injected from the anode into the organic EL layer and an electron is injected from the cathode into the organic EL layer where the hole and electron are re-bonded to each other. By energy occurring at this time, a molecule in the organic light emitting compound making up the organic EL layer is excited. A light emitting phenomenon occurs when the excited molecule is deactivated while being put into a ground state. The organic EL device is a light emitting body using this light emitting phenomenon.
The organic EL layer has a single-layer structure or a multi-layer structure including an organic layer called a light emitting layer in which light is emitted when the hole and electron are re-bonded together and at least one layer out of an organic layer called a hole transporting layer where the hole is easily injected into the organic EL layer and the electron is not easily moved therein and an organic layer called an electron transporting layer where the electron is easily injected into the EL layer and the hole is not easily moved therein.
In recent years, the organic EL device is under rapid development and becomes commercially practical. Such the organic El device is basically constructed so that a thin film made of a hole injecting material such as triphenyldiamine (TPO) or a like is grown, by a deposition method, on a transparent electrode (serving as a hole injecting electrode, that is, as an anode) made from indium tin oxide (ITO) or a like and then on the thin film is formed, in a stacked manner, a light emitting layer made from a fluorescent substance such as alumi-quinolinol complex (Alq3) or a like and on the light emitting layer is further formed a metal electrode (serving as an electron injecting electrode, that is, as a cathode) using such as silver (Ag), magnesium (Mg), or a like which provides a small work function. Such the organic EL device can provide very high luminance of hundreds cd/m2 to ten-thousands cd/m2 by application of a voltage as low as about 10 V, it is expected to be used in electrical components and/or display devices for household electrical appliance, automobiles, two-wheelers, airplanes, or a like. In such the above organic EL device, for example, an organic layer serving as a light emitting layer is put between a scanning (common line) electrode serving as the electron injecting electrode and a data (segment line) electrode serving as the hole injecting electrode, that is, the transparent electrode.
Moreover, the display device using the organic EL device described above can be roughly classified into two types of display devices, one being a matrix-type display device and another being a segment-type display device. In the matrix-type display device, a dot-matrix display is performed by arranging the scanning electrode and data electrode in a matrix form in which information such as an image, character or a like is displayed in a form of an aggregate of pixels made up of dots. In the segment-type display device, a predetermined content for a specified purpose is displayed as an individual and independent display unit having a predetermined shape and size. The segment-type display can be operated by a static driving method to cause the display unit to display individually and separately, however, the dot-matrix display device has to be operated by a dynamic driving method which causes each of the data lines and scanning lines to be driven in a timeshared manner.
The light emitting body making up a light emitting element portion in the organic EL device can be also classified into two types of light emitting bodies, one being a substrate surface light emitting body type and another being a film surface light emitting body type. The substrate surface light emitting body, is so constructed that a transparent electrode is formed on a transparent substrate and a light emitting layer is formed on the transparent electrode and a metal electrode is further formed on the light emitting layer and that light produced in the light emitting layer is transmitted and transferred through the transparent electrode and the transparent substrate to an outside. On the other hand, the film surface light emitting body is so constructed that a metal electrode is formed on a substrate and a light emitting layer is formed on the metal electrode and a transparent electrode is further formed on the light emitting layer and that light produced in the light emitting layer is transmitted and transferred through the transparent electrode and then from a side of a film being placed opposite to a surface of the substrate to the outside. An example of the substrate surface light emitting body is disclosed in a collection of articles titled xe2x80x9cAppl. Phys. Lett., No. 51, pp. 913-915 (1987)xe2x80x9d. An example of the film surface light emitting body is disclosed in the xe2x80x9cAppl. Phys. Lett., No.65, pp. 2636-2638 (1994)xe2x80x9d.
However, a fluorescent organic body used as a material for the light emitting layer in the conventional organic EL device used as the light emitting body or light emitting element is susceptible to moisture, oxygen, or a like. Moreover, a characteristic of the conventional electrode (hereinafter being called a facing electrode) being placed directly on the light emitting layer or with a hole injecting layer or an electron injecting layer being interposed between the light emitting layer and the facing electrode is easily deteriorated by oxidation. Because of this, when the conventional organic EL device is operated in the atmosphere, a characteristic of its light emission is rapidly deteriorated. If oxygen or moisture exists in the vicinity of the conventional organic EL device, organic materials are deteriorated easily by oxidation which causes peeling of the film and growth of a dark spot (non-emitting portion) and, as a result, a phenomenon with which no light is emitted occurs. This presents a problem in that a life of the organic EL device is shortened.
Therefore, in order to obtain a practical organic EL device, some improvements are necessary so that moisture or oxygen does not invade its light emitting layer and so that its facing electrodes are not oxidized.
To solve this problem, a method of encapsulating the organic EL device to seal out the oxygen is disclosed in, for example, Japanese Patent Application Laid-open No. Hei 5-182759, in which an organic EL device is covered with a moisture-resistant light curing resin layer and with a small and low water-permeable substrate being adhered on an upper portion of the light curing resin layer. Another method for encapsulating an organic EL device is disclosed in Japanese Patent Application Laid-open No. Hei 5-41281 in which the organic EL device is put into an inert liquid produced by using a fluorocarbon oil containing a dehydrating agent such as a synthetic zeolite. Still another method of encapsulating an organic EL device is disclosed in Japanese Patent No. 2800813 in which the organic EL device is coated with a fluorine polymer protecting layer on which a sealing portion having a cap structure and being filled with an inert medium is further formed.
However, only by applying such the encapsulating technologies as described above, it is impossible to completely remove moisture and/or oxygen existing in the vicinity of an organic EL device. As a result, it is difficult to secure a sufficient light emitting life of the conventional organic EL device. Another problem is that, if such the conventional method of encapsulating technology is employed, an increase in a thickness of a display device itself using such the organic EL device is inevitable due to an additionally attached sealing material. It is therefore desirous that long light emission lasting time is secured without pig using such the process of encapsulation of the organic EL device.
In view of the above, it is an object of the present invention to provide a light emitting body, light emitting element and light emitting display device making up an organic EL device using the same which are capable of securing longer light emission lasting time by using a process of encapsulation and of securing practical long light emission lasting time even without use of processes of the encapsulation.
According to a first aspect of the present invention, there is provided a light emitting body including:
a substrate;
a transparent electrode;
a light emitting material;
an upper electrode;
wherein the transparent electrode is formed on the substrate and the light emitting material and the upper electrode are formed in order on the transparent electrode;
wherein the transparent electrode is made up of a mixture of an oxide of indium with tin having a structural formula of xe2x80x9cIn2-xSnxO3-yxe2x80x9d as a chief component and a value of the xe2x80x9cyxe2x80x9d is set to be within a range between not less than 0.05 and not more than 0.2.
According to a second aspect of the present invention, there is provided a light emitting body including:
a substrate;
a transparent electrode;
a light emitting material;
a lower electrode;
wherein the lower electrode is formed on the substrate and the light emitting material and the transparent electrode are formed in order on the lower electrode; and
wherein the transparent electrode is made up of a mixture of an oxide of indium with tin having a structural formula of xe2x80x9cIn2-xSnxO3-yxe2x80x9d as a chief component and a value of the xe2x80x9cyxe2x80x9d is set to be within a range between not less than 0.05 and not more than 0.2.
In the foregoing, a preferable mode is one wherein a layer made of a hygroscopic material is formed adjacent to the transparent electrode.
Also, a preferable mode is one wherein a light emitting element portion includes a layer of the transparent electrode, a layer of the light emitting material and a layer of the upper/lower electrode is an electroluminescence device.
Another preferable mode is one wherein the electro-luminescence device using an organic material as the light emitting material has a structure in which light is emitted from a thin film made of the organic material when a current is fed to the thin film.
Also, a preferable mode is one wherein a hole injecting layer is formed between the layer of the transparent electrode and the layer of the light emitting material.
Also, a preferable mode is one wherein an electron transporting layer is formed between the layer of the light emitting material and the layer of the upper/lower electrode.
Also, a preferable mode is one that wherein using the light Ad emitting body according to the first aspect or the second aspect as light emitting element, includes three groups of the light emitting elements including a first light emitting element group, a second light emitting element group and a third light emitting element group, each being independently stacked and each being made up of at least one of the light emitting elements and each being placed in juxtaposition in a plane manner on a substrate wherein the first light emitting element group emits light at a wavelength region for a red color, the second light emitting element group emits light at a wavelength region for a green color and the third light emitting element group emits light at a wavelength region for a blue color.
Also, a preferable mode is one wherein each of the light emitting groups is so configured that light is emitted simultaneously at each of wavelength regions for red, green and blue colors.
Also, a preferable mode is one wherein mixed color light is emitted which contains light in blue, red and green colors produced by each of the plurality of light emitting element groups being placed in juxtaposition in a plane manner on the substrate.
According to a third aspect of the present invention, there is provided a light emitting element portion using as light emitting element the light emitting body according to the first aspect or the second aspect including the layer of the transparent electrode, the layer of the light emitting material and the layer of the upper electrode, the light emitting element portion including the light emitting element and current supplying element used to be connected electrically and feed a current to the light emitting element.
In the foregoing, a preferable mode is one that wherein further includes a switching element connected to the current supplying element which has a function to judge whether or not a current is to be fed to the light emitting element including the layer of the transparent electrode, the layer of the light emitting material, and the layer of the upper electrode.
Also, a preferable mode is one that wherein further includes wirings connected to the current supplying element and used to feed a current to the current supplying element and wirings to supply voltage information about an ON/OFF state to the switching element.
According to a fourth aspect of the present invention, there is provided a light emitting display device having a plurality of the light emitting element portions according to the third aspect, wherein the wirings to feed a current to the current supplying element and wirings to supply voltage information about an ON/OFF state to the switching element are arranged in a matrix form.
With the above configurations, by using a substance xe2x80x9cIn2-xSnxO3-yxe2x80x9d as a material for a transparent electrode layer making up a stacked light emitting body and by setting a value xe2x80x9cyxe2x80x9d to be within a range of 0.06 to 0.2, it is possible to secure a light emission lasting time that can be used practically, that is, to obtain a light emitting body and light emitting element that can improve their light emission life and a light emitting display device using the light emitting body and light emitting element.
With another configuration as above, by using a method of encapsulating the light emitting body and light emitting element, it is possible to lengthen the light emission lasting time and, even without using the encapsulating method, obtain the organic EL device that can provide long light emission lasting time that can be commercially used and a display device using the organic EL device.